Initial low temperature setting in radiofrequency catheter ablation of Wolff-Parkinson-White syndrome

Previous studies have shown that with low temperature testing for RF ablati on of arrhythmias, unnecessary irreversible myocardial lesions may be avoid ed. In children admitted for RF ablation from June 1996 to May 1999, we eva luated the method of an initial temperature setting of 50 degreesC for a ma xim um of 10 seconds. If accessory pathway block occurred, the temperature setting was immediately increased to 70 degreesC and continued for 45-120 s econds (group 1). If accessory pathway block did not occur after several at tempts, subsequent attempts were made with initial settings at 70 degreesC- 80 degreesC at the same or different sites (group 2). Eighty patients with Wolff-Parkinson-White syndrome (mean age 11 +/- 4 years) were treated using this method. Twelve patients were excluded for various reasons. Of the rem aining 68 patients, 52 (76%) had successful block of the pathway at 50 degr eesC; 16 patients demonstrated block only at the higher temperature setting of 70 degreesC-80 degreesC. There were no statistically significant differ ences between these two groups in terms of age, weight, and location of acc essory path ways. Unsuccessful 50 degreesC test ablation attempts were 1.6 +/- 2.4 in group 1 and 3.1 +/- 2.9 in group 2 (P = 0.04). Total unsuccessfu l attempts were 1.6 +/- 2.4 in group 1 and 8.1 +/- 7.1 in group 2 (P = 0.00 1). The time from application of RF energy to the time of AP block in group 1 was not significantly different from group 2. In the majority of childre n, successful RF ablation can be achieved by using a temperature setting of 50 degreesC, then 70 degreesC. This will prevent unnecessary permanent inj ury at unsuccessful attempt sites.